Although many antibacterial agents are tested on free-floating, planktonic cultures of bacteria, these organisms rarely exist this way in nature. More commonly, bacteria are found in complex communities called biofilms. This is especially true in the oral cavity where up to 700 species of bacteria form a complicated mixed species biofilm commonly referred to as dental plaque. Dental plaque may lead to a variety of undesirable conditions, including erosion of the enamel, dental hypersensitivity, halitosis, tooth decay, caries and gingivitis. Relative to free living bacteria, bacteria found in biofilms differ in their metabolic rates, nutrient access and requirements and susceptibility to antimicrobial agents. Agents that are active against bacteria in culture may be relatively ineffective against bacteria in plaque, absent some mechanism to disrupt the biofilm.
Gallium is a transition metal generally found in gallium(III) salt form. Due to its similarity in size and charge to iron, the body handles Ga3+ in many ways as though it were iron, and thus it is bound (and concentrates) in areas of inflammation, such as infection, and also areas of rapid cell division. Gallium salts have thus been used in a number of biomedical applications to target iron-based mechanisms, e.g., as a carrier of radiation for nuclear medicine, to treat pain associated with arthritis, and to treat hypercalcemia sometimes associated with cancer treatment. Gallium is also known to be an antibacterial agent, as it is readily taken up by the iron-scavenging mechanisms of bacterial cells. Most bacteria require iron for survival, but as they often exist in iron-poor environments, they have developed a variety of mechanisms for iron scavenging. When gallium is taken up in place of iron, it cannot be used in the same manner, and it effectively poisons the bacterial cells.
ε-Polylysine is a polymer composed of l-lysine molecules with an amide linkage between the ε-amino and α-carboxyl groups. This compound is a naturally occurring product of microbial fermentation and has been used as a food preservative.
There is a need for safe and effective oral care products which are not only effective against bacteria in a free-floating culture, but are capable of disrupting the biofilm forming dental plaque, and rendering the bacteria susceptible to removal and destruction.